1. Field of the Invention
The present invention relates generally to a pick-up cartridge, and is directed more particularly to a moving magnet type pick-up cartridge in which around a moving magnet there are located coils without any yoke, preferably hollow coils, so that when the magnet is subjected to a movement or vibration, an electro-motive force is generated in the hollow coils without any magnetic distortion by the yoke.
2. Description of the Prior Art
As shown in FIG. 1, a prior art moving magnet type cartridge consists of a cantilever 1, a stylus 2 attached to one end of the cantilever 1 and a magnet 3 attached to the other end of the cantilever 1. When the cantilever 1 and hence the magnet 3 is moved or vibrated in accordance with the sound groove of a record disc, the magnetic field originated from the magnet 3 is changed. This change of the magnetic field is introduced to a yoke 4 and picked up by a coil 5 wound on the yoke 4 from which an output signal is derived. Since the yoke 4 passes through the coil 5, the characteristics of the prior art moving magnet type cartridge become such that the magnetic permeability of the yoke 4 is varied in response to the magnetic field to cause distortion and that as the frequency becomes high an eddy current is generated in the yoke 4 to lower the output signal in a high frequency band. Further, since the coil 5 is wound on the yoke 4, the output impedance increases. Thus, the reproduction characteristic is varied by the influence of a load impedance. While, in the case of a moving coil type pick-up cartridge, since its coil is vibrated in the parallel magnetic field, the above defect of the moving magneti type pick-up cartridge is not caused. However, since in the moving coil type pick-up cartridge its coil is wound on the vibrating system, it is difficult to manufacture the same, its equivalent mass increases and it is also difficult to exchange the resproducing stylus and so on.